Genetic studies have shown that wild-type D-serine deaminase (Dsdase I, dsdA gene product) synthesis in Escherichia coli K12 is controlled by induction and catabolite repression, at the level of transcription. The induction control, which is mediated by the dsdC gene product, appears to be strictly positive. The catabolite repression control is mediated by the cyclic AMP and cyclic AMP binding protein system. The operator locus, dsdO, is the site of action of both the induction and the catabolite repression controls. Our ultimate aim is to define the mechanism by which interaction of the dsdC product and of the cAMP-cAMP binding protein with the promoter-operator effects transcription of dsdA. BIBLIOGRAPHIC REFERENCES: Heincz, M.C., and McFall, E. 1976. Specific in vivo cleavage of D-serine deaminase and properties of tetrameric polypeptide aggregates of the fragments. J. Bacteriol. 126:132-139. Palchaudhuri, S., McFall, E., and Carothers, A.M. 1976. Specialized transduction of D-serine deaminase genes: Formation of lysogens that yield high lamdba d-dsd/lamdba ratios and formation of a dimeric lambda d-dsd. J. Bacteriol. 127:998-1014.